Laser digitizer system for dental applications

ABSTRACT

A intra-oral laser digitizer system provides a three-dimensional visual image of a real-world object such as a dental item through a laser digitization. The laser digitizer captures an image of the object by scanning multiple portions of the object in an exposure period. The intra-oral digitizer may be inserted into an oral cavity (in vivo) to capture an image of a dental item such as a tooth, multiple teeth or dentition. The captured image is processed to generate the three-dimension visual image.

PRIORITY AND CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit under 35 U.S.C. § 119(e) ofco-pending provisional application no. 60/457,025 for Intra-Oral LaserDigitizer System For Dental Applications, which is incorporated in itsentirety herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Related Field

[0003] The invention relates to three-dimensional imaging of physicalobjects. In particular, the invention relates to intra-oral (in vivo)laser imaging of dental items including dentition, prepared dentition,impression materials and the like.

[0004] 2. Description of the Related Art

[0005] A three-dimensional (“3D”) visual image of a physical object maybe generated by a computer that processes data representing shapes,surfaces, contours and/or characteristics of the object. The data isgenerated by optically scanning the object and detecting or capturingthe light reflected from the object. Principles such as Moiré,interferometry, and laser triangulation, may be used to model the shape,surfaces, contours and/or characteristics of the object. The computerdisplays the 3D image on a screen, or computer monitor.

[0006] Existing intra-oral 3D imaging systems use a variation of theMoiré imaging technique. Such systems use structured white light toproject a two-dimensional (“2D”) depiction on the object to be imaged.Moiré systems use the 2D lateral information, and input from skilledoperators, to determine relative dimensions of adjacent features. Moirésystems also use a sinusoidal intensity pattern that is observed from aposition other than a projection angle that does not appear sinusoidal.Therefore, an inferred point-by-point phase angle between an observedand a projected image may be correlated to height data.

[0007] Intra-oral dental imaging systems, based on the Moiré techniqueimage a dental item, such as a tooth, directly from or below occlusalsurfaces of the tooth. Such systems have low depth resolution and maynot accurately image or represent a surface that is undercut orshadowed. Intra-oral dental imaging systems also may require a powder orthe like to provide a uniform color and reflectivity required bylimitations of the white light techniques. The powder layer may increaseor introduce errors in the digitized data, due to non-uniformity of thepowder thickness.

BRIEF SUMMARY OF THE INVENTION

[0008] The embodiments provide a laser imaging system that generates athree-dimensional image of a scanned physical object such as a dentalitem. An embodiment includes intra-oral laser imaging systems, methods,apparatuses, and techniques that provide digitization of a physicalobject to generate a 3D visual image of the object. An intra-oraldigitizer generates a laser pattern that may be projected on or towardsa dental item, dentition, prepared dentition, or impression material inan oral cavity (in vivo). The intra-oral digitizer may include aprojection optics system that remotely generates the laser pattern andrelays that pattern so that it may be projected on or towards a dentalitem or items in vivo. The intra-oral digitizer also includes an imagingoptical system that detects or captures light reflected from the dentalitem. The imaging optical system, or a portion thereof, may be insertedin the oral cavity at a known angle with respect to the projectionsystem to capture light reflected from the dentition. The captured lightmay be used to generate data representative of the 3D image of thedentition. The 3D visual image may be displayed on a computer monitor,screen, display, or the like. The data also may be used to form a dentalrestoration using known techniques such as milling techniques. Therestoration may be a crown, bridge, inlay, onlay, implant or the like.

[0009] The intra-oral laser digitizer may have a light source, afocusing objective, a two-axis scanner, an optical relay system, animage optics system, and a processor configured to carry outinstructions based on code, and process digital data. The light sourcemay have a laser LED and collimating optics producing a collimated beamof light that is projected to the two-axis scanner. The scannerredirects, or scans, the collimated beam of light through at least twoaxes at high speeds. The scanner may scan the beam at a selectedconstant frequency or a variable frequency and duty cycle. The scannedbeam is projected toward the optical relay system, which focuses thebeam as a dot on the surface of the object.

[0010] The optical relay system may include focusing lenses, relaylenses and a prism, through which the scanned beam may be projected. Theoptical relay system focuses the desired pattern of the laser dotgenerated by the scanner on the object. The laser dot may be focused sothat the dot traverses a curvilinear segment across the object. Theoptical relay system may include one or more optical components such asstandard optical glass lenses, or gradient index glass lenses.

[0011] The image capture instrument detects the light reflected from theobject through a relay optics system. The image capture system generatesdata representing a captured image of the scanned beam. The imagecapture system may be configured to capture images of one or morescanned curvilinear segments during an exposure period. The computerprocesses the data to generate the three-dimensional visual image of theobject on a computer monitor, a screen, or other display.

[0012] Multiple images of the object may be recorded and processed bythe computer to produce a 3D map of the object. The multiple images canbe captured from multiple positions and orientations with respect to theobject. The individual images are merged to create an overall 3D map ofthe object. The images may be captured and processed to provide a realtime image of the surface of the object. The real time image may providean instant feedback mechanism to an operator of the system. Thedigitizer system may include software that displays the overall 3D imagecaptured in real time. The software also may include feedback andidentification provided to the operator of suggested viewpoints tocomplete the overall 3D image. The software also may identify crucialfeatures in the scanned data set during a data acquisition process.These features include margins and neighboring dentition. This softwarealso may display highlighted features or possible problem areas, as theoperator captures additional viewpoints.

[0013] A one- or two-axis tilt sensor may determine a relative anglebetween images. The imaging system may also be used as a standard 2Ddental camera through the addition of a background light source.

[0014] Control, acquisition, and interaction may be initiated via footcontrols, controls on the intra-oral device, or by voice recognition ofspoken commands, or like methods.

[0015] An embodiment quickly and accurately digitizes 3D surfaces of anobject, such as prepared teeth and impression materials including biteregistration strips. The intra-oral digitizer also provides improvedimaging abilities over prior art intra-oral dental imaging systems. Thedigitizer also simplifies operator requirements and interactions for anintra-oral dental scanning system.

[0016] Other systems, methods, features and advantages of the inventionwill be, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description, be within the scope ofthe invention, and be protected by the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention can be better understood with reference to thefollowing drawings and description. The components in the figures arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention. Moreover, in the figures,like referenced numerals designate corresponding parts throughout thedifferent views.

[0018]FIG. 1 illustrates an intra-oral laser digitizer coupled to aprocessor.

[0019]FIG. 2 illustrates a front view of a portion of the intra-orallaser digitizer of FIG. 1.

[0020]FIG. 3 illustrates a top view of the intra-oral laser digitizer ofFIG. 1.

[0021]FIG. 4 illustrates a side view the intra-oral laser digitizer ofFIG. 1.

[0022]FIG. 5 illustrates an imaging optical system of the intra-orallaser digitizer of FIG. 1.

[0023]FIG. 6 illustrates a projection optics system of the intra-orallaser digitizer of FIG. 1.

[0024]FIG. 7 illustrates a projection of a laser light beam on anobject.

[0025]FIG. 8 illustrates a top view of a projection of a laser lightbeam.

[0026]FIG. 9 illustrates a two-axis scanner of the intra-oral laserdigitizer of FIG. 1.

[0027]FIG. 10 illustrates an image of a light pattern of the intra-oraldigitizer, as projected on and viewed from a flat surface.

[0028]FIG. 11 illustrates the light pattern of FIG. 10 as projected onan object to be imaged.

[0029]FIG. 12 illustrates a reflection of the light pattern of FIG. 10as detected by image capture instrument.

[0030]FIG. 13 illustrates multiple laser profiles projected towards anobject.

[0031]FIG. 14 illustrates an electronic circuit that for controlling thegeneration of a line pattern.

[0032]FIG. 15 illustrates an intra-oral digitizer with a low coherencelight source coupled to the scanning system and a coupler to a referencebeam on an optical delay line.

DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

[0033]FIG. 1 illustrates an example of an intra-oral laser digitizer100. FIGS. 2-5 illustrate various views of the intra-oral laserdigitizer 100 of FIG. 1. The intra-oral digitizer 100 generates a 3Dimage of an object 108 such as a dental item. The intra-oral digitizer100 generates a laser pattern that may be projected on or towards adental item, dentition, or prepared dentition in an oral cavity (invivo). The intra-oral digitizer 100 may remotely generate the laserpattern and relay the pattern towards the dental item or items in vivo.The laser pattern may be relayed through relay optics such as prisms,lenses, relay rods, fiber optic cable, fiber optic bundles, or the like.The intra-oral digitizer 100 also may detect or capture light reflectedfrom the dental item in vivo. The intra-oral digitizer 100, or a portionthereof, may be inserted in the oral cavity to project the laser patternand to detect the reflected laser pattern from the dental item or itemsin the oral cavity. The captured light may be used to generate datarepresentative of the 3D image of the dentition. The data may be used todisplay the 3D image. The data also may be used to form a model of theobject using known techniques such as milling techniques. The model ofthe object may be a dental restoration such as a crown, bridge, inlay,onlay, implant or the like. The data also may be used for diagnosticpurposes.

[0034] The laser digitizer 100 includes a laser light source 101, afirst scanner 102 (x scanner), a second scanner 103 (y scanner), a lensassembly 104, a first reflecting prism 113, a first optics relay 105, asecond reflecting prism 107, a third reflecting prism 106, a secondoptics relay 109, imaging optics assembly 110, imaging sensor 111, andan electronic circuit 112. The intra-oral laser digitizer 100 may becoupled to a processor 119.

[0035] The laser light source 101 may include collimating optics (notshown) that generate a laser beam of light 122 from the light source101. The collimated light beam 122 is characterized by parallel rays oflaser light. The laser beam 122 is projected to the first scanner 102.

[0036] The laser light source 101 may include a laser diode or LED thatgenerates a laser light beam having an elliptical-shaped cross-section.The collimating optics may be configured to circularize the ellipticalbeam and to generate a circular spot. The circular spot may be used toscan a uniform line across the surface of the object 108. The laserdiode may be any commercially available laser diode configured to emit alaser light beam, such as the Blue Sky Research Mini-Laser 30 mWattlaser with 0.6 mm collimated beam, model number Mini-635D3D01-0.

[0037] The laser light source 101 also may modulate the laser lightbeam. The laser light source 101 may be coupled to a modulator thatadjusts or interrupts light flow from the source at high modulation orswitching rate. The modulation may be in the range of substantially 1kHz to substantially 20 MHz. A scan pattern may be generated on theobject, by modulating the laser light source 101.

[0038] The first scanner 102 includes an x-scanner mirror having asubstantially flat reflecting surface. The reflecting surface of thex-scanner mirror, may be rectangular-shaped having dimensionsapproximately 1.5 mm by approximately 0.75 mm. The laser beam 122 fromthe light source 101 may have a width no greater than the smallestdimension of the first scanner 102. For example, the width of the laserbeam may be approximately 0.6 mm. The beam of light 122 from the laserlight source 101 is incident upon the reflecting surface of the firstscanner 102.

[0039] The second scanner 103 includes a y-scanner mirror having asubstantially flat reflecting surface. The reflecting surface of they-scanner mirror, may be rectangular-shaped having dimensionsapproximately 1.5 mm by approximately 0.75 mm. The reflecting surfacesof the x-scanner and the y-scanner may be mirrors or the like.

[0040]FIG. 2 illustrates the second scanner 103 positioned substantiallyorthogonal to the first scanner 102. The first scanner 102 directs thebeam of light 122 towards the second scanner 103. The beam 122 directedfrom the first scanner 102 is incident upon the reflecting surface ofthe second scanner 103. The first scanner 102 directs the beam 122 alongan arc onto the reflecting surface of the second scanner 103. Thereflective surface of the first scanner 102 may be rotated through anaxis of rotation to create the arc on the reflective surface of thesecond scanner 103. Together, the reflecting surfaces of the firstscanner 102 and the second scanner 103 form a two-axis scanner assembly116. The reflective surface of the second scanner 103 rotates throughthe y-axis to direct a two-axis scanned beam 124 in an orthogonaldirection.

[0041] The scanned beam 124 is incident upon the lens assembly 104. Thelens assembly 104 focuses the scanned beam 124 through the firstreflecting prism 113. The first reflecting prism 113 directs a scannedimage 125 to the first optics relay 105.

[0042]FIG. 3 illustrates the first optics relay 105 relaying the scannedimage 125 to the second reflecting prism 107. The second reflectingprism 107 may be inserted into an oral cavity to project the laserpattern toward one or more dental items to be imaged. The first opticsrelay 105 transmits the laser pattern generated by the light source 101,the first and second scanner 102, 103 and the lens assembly 104 to aremote location, such as an oral cavity. The second reflecting prism 107projects a scanned beam 114 towards the object 108 so that a lightpattern may be projected on the object 108. The first optics relay 105may be any commercially available relay optics system. The first opticsrelay 105 may be a relay lens such as a GRIN lens, a fiber optic cable,a fiber optic bundle, or similar device for relaying an optical imageover a distance L1. An example of a first optics relay 105 is a GrinTechrod lens with part number 12534082-4C-9 attached to the GrinTechobjective grin lens with part number CR1032-2.

[0043] As shown in FIG. 4, a reflection 115 of the scanned beam 114 fromthe surface of the object 108 is captured through the third reflectingprism 106 to relay captured reflection 126. The third reflecting prism106 may be inserted into an oral cavity to detect or capture reflectionsof the laser pattern from the one or more dental items to be imaged. Thesecond optics relay 109 transmits captured reflection 126 for a distanceL2 from the oral cavity to the imaging optics assembly 110. The capturedreflection 126 from the object 108 is imaged and focused by the imagingoptics 110 to provide a focused beam 127. The focused beam 127 isprojected towards the imaging sensor 111. The imaging sensor 111 may bea CCD sensor, a CMOS sensor, or other light sensitive device or array oflight sensitive devices. The second optics relay 109 may be anycommercially available relay optics system. The second optics relay 109may be a relay lens such as a GRIN lens, a fiber optic cable, a fiberoptic bundle, or similar device for relaying an optical image over adistance L2. An example of the second optics relay 109 is the GrinTechrod lens with part number 12534082-4C attached to the GrinTech objectivegrin lens with part number CR1032-2.

[0044] The imaging sensor 111 may be coupled with electrical circuit112. The electrical circuit 112 may include electrical and electroniccomponents suitable for processing electrical signals of the intra-oraldigitizer 100. The electrical circuit 112 may be located or enclosedwithin a suitable enclosure. The enclosure may be a hand-held enclosureor have a form factor suitable for being handheld, for enclosing theelectrical circuit 112 and for manipulating the intra-oral digitizer 100in vivo. The enclosure and electrical circuit may be remotely locatedfrom the second and third reflecting prisms 107, 106. The electricalcircuit 112 may modulate the light source 101, and drive the scanningmirrors 102 and 103. The electrical circuit also may gather electronicdata received from the imaging sensor 111. The electrical circuit alsomay perform additional processing and communication with an externalprocessor 119 via a cable or wireless or some other communications link.

[0045]FIG. 5 illustrates an imaging optics system 120 of the laserdigitizer 100. The imaging optics system 120 may include the thirdreflecting prism 106, the second optics relay 109, the imaging optics110 and the imaging sensor 111. The imaging optics system 120 generatesa digital signal representative of the capturer reflection 126.

[0046]FIG. 6 illustrates the projection optics system 121, including thelens assembly 104, the first reflecting prism 113, the first opticsrelay 105, and the second reflecting prism 107. The projection opticssystem 121 may project the scanned image in the direction of the theobject 108 so as to project the laser pattern in vivo.

[0047]FIG. 7 illustrates a front view of a portion of the intra-orallaser digitizer 100. The scanned beam 114 is directed from theprojection optics system 121 in the direction of the object 108.Reflected light 115 is captured or detected by the imaging optics system120. The imaging optics system 120 may be characterized by a coordinatesystem having axes X, Y, Z and the projection optics system 121 may becharacterized by a coordinate system having axes X′Y′Z′. The Z′ axisprojects vertically from a center of the second reflecting prism 107 tothe object 108, and Z is the axis projected vertically from the surfaceof the object at 108 to a center of the third reflecting prism 108. TheX′ axis is orthogonal to the Z′ axis and in a horizontal plane withrespect to the front of the intra-oral device 100. The X axis isorthogonal to the Z axis. The Y′ axis may be defined according to the X′axis and the Z′ axis in a right-handed coordinate system, as illustratedin the top view of the second reflecting prism 106 and the thirdreflecting prism 107, as illustrated in FIG. 8. The Y axis may bedefined according to the X′ axis and the Z′ axis in a right-handedcoordinate system, as illustrated in the top view of the secondreflecting prism 106 and the third reflecting prism 107, as illustratedin FIG. 8.

[0048] An angle between the Z axis and Z′ axis may be designated as θ. Adistance from a center of the third reflecting prism 106 to the point onthe object 108 may be referred to as d1 and a distance from the centerof the third reflecting prism 106 to a top of a depth of focus regionmay be referred to as d2.

[0049]FIG. 9 illustrates a two-axis scanner assembly 116. The two-axisscanner assembly may include the first scanner 102 and the secondscanner 103. The first scanner 102 includes a reflective surface thatrotates about axis 117. The reflective surface of the first scanner 102directs the light to the reflecting surface of the second scanner 103.The reflective surface of the second scanner 103 rotates about the axis118.

[0050] The reflective surfaces of the scanners 102 and 103 may berotatably coupled with a respective motor, other electromagnetic drivingmechanism, or electrostatic driving mechanism such as magnets, coils orother electromagnetic coupling that control a rotational movement of thecorresponding reflective surface to effect the scanning of thecollimated light beam.

[0051] The two-axis scanner 116 redirects, or scans, the collimatedlight beam to form a scanned light beam 114 having a position thatvaries over time. The scanned beam 114 is directed by the two-axisscanner 116 to the lens assembly 104 and the first optics relay 105. Thetwo-axis scanner 116 redirects the collimated light beam in at least twoor more axes 117, 118 where each axis is substantially perpendicular tothe axis of the collimated light beam. The first and second scanners102, 103 may have essentially perpendicular axes, and may be essentiallyorthogonal with respect to each other. The scanners 102, 103 also may bepositioned at an arbitrary angle relative to each other.

[0052] Additional scanners also may be included to scan the collimatedlight beam. The scanners 102, 103 may be positioned orthogonally so thatthe collimated laser beam incident on the reflectors may be scanned orredirected in at least two axes. The first scanner 102 scans the beamalong one axis, such as an x-axis. The second scanner 103 may bepositioned so that the beam along the x-axis incident upon the secondscanner 103 may be scanned along an orthogonal direction to the x-axis,such as a y-axis. For example, the first and second scanner 102, 103 maybe positioned orthogonal with respect to each other so that the firstscanner 102 scans the beam along the x-axis and the second scanner 103scans the beam along an orthogonal direction to the x-axis, such as ay-axis.

[0053] The first scanner 102 also may have a spinning polygon mirrorsuch that the rotatable second reflector 103 and the spinning polygonreflector 102 together also are configured to scan the laser beam in twoaxes. The spinning polygon mirror 102 may scan the collimated light beamalong an x-axis and the rotatable mirror 103 may scan the collimatedlight beam along a y-axis. Each axis, the x-axis and y-axis, may besubstantially orthogonal with one another to generate a scanned lightbeam along two substantially orthogonal axes.

[0054] The two-axis scanner 116 also may include a single reflectingsurface that scans a beam of light along two axes. The reflectingsurface may be driven electromagnetically or electro-statically torotate the reflecting surface about two essentially orthogonal axesindividually or simultaneously.

[0055] The two-axis scanner 116 may be include one or moreMicroelectro-mechanical systems (“MEMS”), which have reflecting surfacesthat may be driven electromagnetically or electro-statically or using apiezo crystal or otherwise mechanically to rotate the reflecting surfaceabout two essentially orthogonal axes individually or simultaneously.

[0056] The two-axis scanner 116 also may include a programmable positioncontroller. The position controller may be a component of the two-axisscanner 116 or may be incorporated with the electronic circuit 112. Thecontroller may control movement of the scanners 102, 103 by providingcontrol signals to the drive mechanisms of the reflective surfaces ofthe scanners 102, 103. The controller controls the movement of thescanners 102, 103 so that the collimated laser beam is redirected toprovide to a scan sequence. The coordinate system for the two-axisscanner 116 is referred to as X′Y′Z′.

[0057] As shown in FIGS. 7 and 8, the object 108 to be imaged ispositioned within a field of view of projection optics 121 and theimaging optics system 120. The projection optics 121 is positioned atthe angle θ with respect to an optical axis of the imaging optics system120 so that when the focused dot is scanned across the surface of theobject 108 the light is reflected towards the imaging optics system 120at angle θ. The two-axis scanner 116 moves the scanned beam 114 so thatthe focus point of the laser dot from the projection optics 121traverses through a pattern across the surface of the object 108.

[0058] The imaging optics system 120 may be configured and/or positionedto have a field of view that includes the focused laser dot projected onthe object 108. The imaging optics system 120 detects the laser dot asit is scanned across the surface of the object 108. The imaging opticssystem 120 includes an image sensor 111 that is sensitive to the lightreflected from the object 108. The imaging optics system 120 may includean imaging lens 110 and an image sensor 111 and the second optics relay109 and a prism or fold mirror 106. The imaging lens 110 is configuredto focus the light reflected from the object 108 towards the imagesensor 111. Based on a light detected from the object 108, the imagesensor 111 generates an electrical signal representative of the surfacecharacteristics (e.g., the contours, shape, arrangement, composition,etc.) of the object 108.

[0059] The image sensor 111 captures an image of the scanned surface ofthe object 108. The image sensor 111 may be a photo-sensitive or lightsensitive device or electronic circuit capable of generating signalrepresentative of intensity of a light detected. The image sensor 111may include an array of photodetectors. The array of photodetectors maybe a charge coupled device (“CCD”) or a CMOS imaging device, or otherarray of light sensitive sensors capable of generating an electronicsignal representative of a detected intensity of the light. The imagesensor 111 may comprise a commercially available CCD or CMOS highresolution video camera having imaging optics, with exposure, gain andshutter control, such as the Silicon Imaging USB Camera SI-1280F-U.

[0060] Each photo-detector of the image sensor 111 generates an electricsignal based on an intensity of the light incident or detected by thephoto-detector. In particular, when light is incident to thephoto-detector, the photo-detector generates an electrical signalcorresponding to the intensity of the light. The array ofphoto-detectors includes multiple photo-detectors arranged so that eachphoto-detector represents a picture element, or pixel of a capturedimage. Each pixel may have a discrete position within the array. Theimage capture instrument 120 may have a local coordinate system, XY suchthat each pixel of the scanned pattern corresponds to a uniquecoordinate (x,y). The array may be arranged according to columns androws of pixels or any other known arrangement. By virtue of position ofthe pixel in the array, a position in the image plane may be determined.The imaging optics system 120 converts the intensity sensed by eachpixel in the image plane into electric signals that represent the imageintensity and distribution in an image plane.

[0061] The CMOS image sensor may be configured to have an array of lightsensitive pixels. Each pixel minimizes any blooming effect such that asignal received by a pixel does not bleed into adjacent pixels when theintensity of the light is too high.

[0062] The two-axis scanner 116 may be configured to scan the laser beam114 across the surface of the object 108 via the projection optics 121in various patterns. The pattern may cover a portion of the surface ofthe object 108 during a single exposure period. The pattern also mayinclude one or more curves or any known pattern from which thecharacteristics, elevations and configurations of the surface of theobject 108 may be obtained.

[0063] During an exposure period, an image of a portion of the surfaceof the object is captured. The beam 114 scans the object 108 via thetwo-axis scanner 116 and the projection optics 121 in a selectedpattern, allowing the imaging sensor 111 to detect the light reflectedfrom object 108. The image sensor 111 generates data representative ofthe surface characteristics, contours, elevations and configurations ofthe scanned portion or captured image. The data representation may bestored in an internal or external device such as a memory.

[0064]FIG. 10 illustrates an example of a scanned pattern of light 1048as viewed from a substantially flat surface. The scanned pattern 1048may include multiple curves 1050-1055 that are generated by the scanner116. A portion of the curves 1050-1051 may be essentially parallel toeach other. The curves 1050-1055 also may represent or include aconnected series of points or curvilinear segments where a tangentvector n at any single point or segment obeys the following rule:

|n·R|≠0  (1)

[0065] where R is a triangulation axis that is substantially parallel toY and Y′ and passes through an intersection of an axial ray from thethird reflecting prism 106 of the image optics system 120 and an axialray from the second reflecting prism 107 of the optical projectionsystem 121. Accordingly, the angle between the tangent n at any point orsegment of the curve and the triangulation axis R is not 90 degrees.Each curve 1050-1055 also may have a cross-sectional intensitycharacterized by a function that may have a sinusoidal variation, aGaussian profile, or any other known function for cross-sectionalintensity. In an embodiment, a minimum angle between a valid ray betweenthe second reflecting prism 107 relative to a valid axial ray of thethird reflecting prism 106 is non-zero.

[0066] During a subsequent scan period, the beam 114 is scanned in apattern across an adjacent portion of the object 108 and an image of theadjacent portion is captured. The scanned beam 114 may scan a differentarea of the surface of the object 108 during subsequent exposureperiods. After several exposure periods in which the beam 114 is scannedacross the various portions of the object 108 and images of thosescanned portions captured, a substantial portion of the object may becaptured.

[0067] The processor 119 may be coupled to the imaging optics system 120and configured to receive the signals generated by the image captureinstrument 120 that represent images of the scanned pattern on theobject 108. The processor 119 may process and display the signalsgenerated by the image optics system 120. The processor 119 also may becoupled to the laser light source and control selected or programmedapplications of the laser light. The processor 119 also may be coupledwith the two-axis scanner 116 and programmed to control the scanning ofthe collimated light.

[0068] The image optics system 120 may be characterized by a localcoordinate system X, Y, Z, where the X and Y coordinates may be definedby the image imaging optics system 120. A value for the Z coordinate maybe based on the distance d₁ and d₂ so that d₁≦z≦d₂. A point from aprojected curve incident to a plane perpendicular to Z will appear to bedisplaced in the X direction by Δx.

[0069] Based on a triangulation angle, the following condition mayexist: $\begin{matrix}{{\Delta \quad z} = \frac{\Delta \quad x}{{Tan}\quad \theta}} & (2)\end{matrix}$

[0070] For a given curve (e.g. curve 1050) in the projection patternthere may be unique relations θ(y), z_(base)(y) and x_(base)(y). Therelations θ(y), z_(base)(y) and x_(base)(y) relations may be determinedthrough calibration. The calibration may be performed for example byobserving the curve 1050 as projected on a plane surface. The planesurface may be perpendicular to the imaging optics system 120 at two ormore distances d along the Z axis from the image optics system 120. Foreach y value along the curve 1050, using at least two such curves withknown z values of z₁ and z₂, where z₁<z₂, Δz may be computed asΔz=z₂-z₁. A value Δx may be observed using imaging optics system 120.Using equation (2), θ(y) may be computed. The corresponding valuez_(base)(Y) may be set equal to z₁. The corresponding value X_(base)(Y)may be equal to an x value at the point y on the curve corresponding toz₁. Additional curves may be used to improve accuracy of throughaveraging or interpolation.

[0071]FIG. 11 illustrates the scanned pattern of light 1148 projected onthe object 1180 to be imaged. FIG. 12 illustrates the light patternreflected from the object 1180 as incident to the image sensor 1234. Forthe observed projected curves 1250-1255 on the object, each curvecorresponds to one of the curves 1150-1155 shown in FIG. 11 and acorresponding one of the curves 1050-1055 shown FIG. 10. Accordingly,for each curve 1250-1255, the corresponding relations θ(y), z_(base)(Y)and x_(base)(y) may be selected that were pre-computed during acalibration. For each point (x_(observed), y_(observed)) on each curve1250-1255,

Δx=x _(observed) −x _(base)(y _(observed))  (3)

[0072] Equation (2) may be used to determine Δz using θ(Y_(observed)),and consequently

z _(observed) =Δz+z _(base)(y _(observed))  (4)

[0073] The collection of points (x_(observed), y_(observed),z_(observed)) obtained, form a 3D image of the object 1180.

[0074] A maximum displacement for a curve may be determined by:

Δx=(d ₁ −d ₂)Tanθ  (4)

[0075] A maximum number n_(max) of simultaneously distinguishable curves1050 may be determined according to n_(max)=X_(max)/Δx or equivalently$\begin{matrix}{n_{\max} = \frac{X_{\max}}{\left( {d_{1} - d_{2}} \right){Tan}\quad \theta_{\max}}} & (5)\end{matrix}$

[0076] The number n_(max) increases with a decreasing depth of fieldd₁-d₂ and increases with a smaller θ_(max). The accuracy of thedetermination also may decrease with smaller θ_(max) values.

[0077] Where the number of curves n exceeds n_(max), any ambiguity inthe labeling of the lines may be resolved by associating the observedcurves into groups of adjacent curves. For each group of adjacentcurves, if at least one curve is correctly labeled, then all othercurves in that group may be labeled using adjacency. A method todetermine the correct labeling of at least one curve in a group mayinclude considering a second pattern where the number of curves is lessthan n_(max) and may be at an angle relative to the first pattern. Thecurves of the second pattern may be properly labeled, and intersectionsof the curves of the second pattern with the curves of the first patternmay be used to deduce labeling of some subset of the curves in the firstpattern. This may be repeated with additional patterns until all curvesare correctly labeled.

[0078]FIG. 13 illustrates scanned lines 1350-1352 on the surface of anobject. The scanned line 1350 has associated with it a region bounded bythe boundary curves 1360 and 1362. The region bounded by boundary lines1360 and 1362 is determined by a pre-scan event or calibration data, sothat the scanned line 1350 may be identified separately from otherscanned lines, such as an adjacent line 1352. Adjacent line 1352 isassociated with it its own region bounded by 1364 and 1366. Multiplescanned lines may be projected simultaneously, where each scanned lineis uniquely identified, even when projected onto a surface that is notsubstantially flat.

[0079]FIG. 14 illustrates an example of a pattern-projection system1470. The pattern-projection system 147 may be incorporated with, partof or a component of the electrical circuit 112. The pattern-projectionsystem 1470 includes a scanner mirror driver circuit 1472 and a laserdriver circuit 1474. The mirror driver circuit 1472 includes a RAM-basedarbitrary waveform generator (AWG) 1476, 1477 and a transconductancepower amplifier stage 1478, 1480 corresponding to a scanner 1482, 1483.

[0080] The AWG 1476 corresponding to a high speed scanner 1482 includesa 16-entry waveform table 1484 and a 12-bit digital-to-analog converter(DAC) 1486. The waveform table 1484 may be incremented at approximately320 KHz to produce a sinusoidal waveform of approximately 20 KHz.

[0081] The AWG 1477 corresponding to a low-speed scanner 1483 includes a666-entry waveform table 1485 and a 12-bit DAC 1487. The waveform table1485 is incremented once per high-speed mirror cycle to produce asinusoidal waveform of approximately 30 Hz. The two AWGs 1476, 1477create a repeating raster pattern at approximately 30 frames per second.Electrical signals synchronize a camera system to the scanner driver. Areference input to each DAC 1486, 1487 is driven by a variable voltage1492, 1493 to dynamically adjust the horizontal and vertical dimensionsof the raster.

[0082] The high-speed scanner 1482 is driven at a resonance frequency inthe range of about 20 KHz. A position feedback signal of the scanner1482 may be used with a closed-loop control using a DSP 1495 and a DDS1496 to adjust drive frequency of the drive signal to track variation inthe resonance frequency. The frame rate of the raster pattern may changewith the high-speed resonance frequency of the scanner 1482. An exampleof the DSP includes model number TMS320LF2407A by Texas Instruments. Anexample of the DDS includes model number AD9834 by Analog Devices.

[0083] The laser driver circuit 1470 may include a multiple-bank randomaccess memory (RAM)-based pattern table 1488 and a laser diode currentmodulator 1490. The RAM-based pattern table 1488 includes multiple banksof memory, where each bank includes a bit-mapped pixel image to bedisplayed during a single-pattern frame. A counter synchronized with theraster of the scanner raster generator accesses the pattern table 1488and to present the pixel data to the laser diode current modulator 1490to produce a repeating pattern. Each bank of the pattern table 1488 maybe loaded with a discrete pattern. Multiple single-pattern frames may becombined into repeating multiple-frame sequences with linked-listmechanism.

[0084]FIG. 15 illustrates a laser digitizer 1500 configured as anoptical coherence tomography (“OCT”) or confocal sensor. The laserdigitizer includes a fiber-coupled laser 1511. The laser source 1511 maybe a low coherence light source coupled to a fiber optic cable 1510,coupler 1509 and detector 1501. The coupler, an optical delay line 1505and reflector 1504 return delayed light to the coupler 1509. The coupler1509 splits the light from the light source into two paths. The firstpath leads to the imaging optics 1506, which focuses the beam onto ascanner 1507, which steers the light to the surface of the object. Thesecond path of light from the light source 1511 via the coupler 1509 iscoupled to the optical delay line 1505 and to the reflector 1504. Thissecond path of light is of a controlled and known path length, asconfigured by the parameters of the optical delay line 1505. This secondpath of light is the reference path. Light is reflected from the surfaceof the object and returned via the scanner 1507 and combined by thecoupler 1509 with the reference path light from the optical delay line1505. This combined light is coupled to an imaging system 1501 andimaging optics 1502 via a fiber optic cable 1503. By utilizing a lowcoherence light source and varying the reference path by a knownvariation, the laser digitizer provides an Optical Coherence Tomography(OCT) sensor or a Low Coherence Reflectometry sensor. The focusingoptics 1506 may be placed on a positioning device 1508 in order to alterthe focusing position of the laser beam and to operate as a confocalsensor.

[0085] Although embodiments of the invention are described in detail, itshould be understood that various changes, substitutions and alterationscan be made hereto without departing from the spirit and scope of theinvention as described by the appended claims. The laser source mayinclude a laser or LED, and the collimating optics may include opticsthat circularize the generally elliptical beam produced by such sources.This system may produce a circular spot on the object to provide agenerally uniform line when the beam scanned across the object.

[0086] The light source may positioned proximate to the intra-oral laserdigitizer remotely through a light guide such as optical fiber. Thelight source may be remote from the sensor structure and to provide foran intra-oral device having smaller dimensions.

[0087] A second light source (LED, incandescent bulb, laser, or other)may provide a background light so that the intra-oral laser digitizermay be used as a standard 2D dental camera. This second light source maybe located at or near the imaging optical path. The second light sourcealso may be placed remote to the sensor structure with the light broughtto the optical path through a light guide.

[0088] The intra-oral system also may include a one- or two-axis tiltsensor. The computer may monitor the angles of the tilt sensor, and thereceived images of the scanned lines to determine a profile for theobject. A one-, two- or three-axis accelerometer may determineapproximate position changes of the intra-oral digitizer in one, two orthree axes.

[0089] The system also may include a laser light source having a highspeed modulation system. The modulation system switches the laser on andoff at a high rate (typically several MHz), reducing the coherence ofthe laser source and degree of speckle produced by the laser source onthe object.

[0090] The scanning system may include a single mirror that scans in twoorthogonal axes or other non-parallel arrangement. An example of such amicro-mirror scanner is the bi-axial MEMS scanner of Microvision ofWashington. The scanning system may include two mirrors that scan in twoorthogonal directions or other non-parallel arrangement.

[0091] The imaging sensor may be CMOS sensor or a CCD sensor thatcaptures images at high speeds. A processor processes captured images,such that if the probe moves relative to the object, the softwareadjusts the captured data so that an accurate digitization occurs. Theimaging system may include a small image sensor and objective lensmounted directly at the end of the sensor probe to provide a smallerintra-oral probe through elimination of the relay lenses.

[0092] The laser source may include a laser source and line generatingoptics. This laser source produces one or more lines directed to a oneaxis laser scanner to provide for a low speed scanner or no scannerbased on the line generating optics producing sufficient number ofseparate line segments.

[0093] The imaging system may include an objective, relay lens,asymmetric lens system, and a linear sensor array. A linear sensor arrayor analog position sensor may be read for each pixel position. Theasymmetric lens images the scanning field onto the line detector. Thetriangulation angle causes the laser spot to be imaged onto differentelements of the line detector as the object height changes, allowingfast scanning of the object.

[0094] A series of imaged laser segments on the object from a singlesample position interlace between two or multiple 3D maps of the samplefrom essentially the same sample position. The time period to measureeach interlaced 3D map is reduced to a short interval and relativemotion effects between the intra-oral device and the patient arereduced. The interlaced 3D maps may be aligned with software to producean effective single view dense 3D point cloud that has no motion inducedinaccuracies or artifacts. For example, in a 10 step interlacing scheme,each image may be captured in {fraction (1/30)}^(th) of a second. Whenscanning over 0.3 seconds, the present invention reduces affects ofoperator motion. The motion of the operator between each subframe may betracked mathematically through reference points in the dataset itself.The operator motion is removed in subsequent analysis, allowing a systemwith a framerate significantly lower than would otherwise be required.

[0095] Multiple dense 3D point clouds also may be acquired fromapproximately the same position, and mathematically aligned (i.e., movedrelative to each other to minimize the distance between them so as tocause related features in each to become superimposed), and statisticalmethods used to further improve the accuracy of the data (for example,Gaussian filtering).

[0096] A low resolution pre-scan of the surface determines approximategeometry. Referring to this pre-scan, an approximate envelope ofsubsequent laser lines is determined by performing inverse calculationof a laser line centroid to 3D coordinate. Since these envelopes are notrectangular and combined with the assumption that the surface does notchange dramatically locally one can greatly increase the number ofsimultaneous lines projected on the surface and identifiable in theimage, increasing the effective scanning rate. In and example of N linesbeing scanned simultaneously with a system capable of processing Fframes per second, an effective F*N frames per second processing rate,or multiplied by a factor of N, may be achieved.

[0097] The imaging system may be located remotely from the imagingsensor. Through relay optics such as a coherent fiber imaging bundle,the scanning system may be located remotely from the imaging sensor. TheFourier transform of the object image is transferred through the fiberimaging bundle. By transferring the Fourier transform through the fiberbundle, more of the high frequency components of the object imageremain. Also, the effects of the fiber bundle can be removed by removingthe frequency components from the Fourier transformed image, whichcorresponds to the fiber bundle.

[0098] While various embodiments of the invention have been described,it will be apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible within the scope of theinvention. Accordingly, the invention is not to be restricted except inlight of the attached claims and their equivalents.

What is claimed is:
 1. An intra-oral laser digitizer comprising: a lightsource having collimating optics configured to generate a collimatedbeam of light; a scanner optically coupled to the light source andconfigured to scan the collimated beam along at least two axes; anoptics relay coupled to the scanner and configured to relay the scanned,collimated beam towards a remote object to be imaged; an image opticssystem having an optical axis configured to detect a reflection of thescanned beam from the object at an angle θ with respect to the opticsrelay and to generate data representative of a surface of the objectbased on the reflected beam; and a processor coupled to the scanner andthe image optics system configured to generate a three-dimensional imageof the object based on the data.
 2. The intra-oral laser digitizer ofclaim 1 where the light source comprises a laser LED.
 3. The intra-orallaser digitizer of claim 1 where the scanner comprises a plurality ofmirrors.
 4. The intra-oral laser digitizer of claim 3 where the imageoptics system comprises: an image sensor configured to detect atriangulation image of the object, the triangulation image based on aplurality of curves generated by scanning the beam of light on theobject during an exposure period; and an imaging lens system configuredto focus the plurality of curves on the image sensor.
 5. The intra-orallaser digitizer of claim 4 where the processor is configured to mergemultiple images of the object to generate a three-dimensional map of theobject.
 6. The intra-oral laser digitizer of claim 5 where the objectcomprises any one of an in vivo dental item, a dental preparation, adental model, a dental mold, or a dental casting.
 7. The intra-orallaser digitizer of claim 1 where the scanner comprises a single mirrorconfigured to scan the light along at least two-axes.
 8. The intra-orallaser digitizer of claim 1 where the scanner comprises a rotatablemirror and a spinning polygon mirror.
 9. The intra-oral laser digitizerof claim 1 where the scanner further comprises a programmable positioncontroller configured to control the scan of the collimated laser beamin a programmed scan sequence.
 10. The intra-oral laser digitizer ofclaim 1 where the known pattern comprises a plurality of curves each issubstantially parallel to each other.
 11. The intra-oral laser digitizerof claim 1 where the laser light source comprises a low coherence lightsource, the reflected light from the object being compared with lightfrom the low coherence source reflected from a known variable pathlength.
 12. The intra-oral laser digitizer of claim 1 further comprisinga voice-recognition means for controlling operation of the intra-orallaser digitizer in response to voice commands of an operator.
 13. Adental imaging system, comprising: means for generating a collimatedlaser beam of light; scanner means for generating a multi-axiscollimated light beam; beam relaying means for relaying the collimatedlight beam towards an object to be imaged, the object to be imaged beingremotely located from the means for generating a collimated laser beamof light; image capturing means for detecting reflections of the afocused beam projected on an object; and processor means coupled to thescanner means and the image capturing means for generating athree-dimensional image of the object.
 14. The laser digitizer of claim13 where the scanning means scans the beam across the object in aselected pattern via beam relaying means.
 15. The laser digitizer ofclaim 13 where the image capturing means comprises: an image sensorconfigured to detect a triangulation image of the object, where thetriangulation image is based on a pattern of scanned lasers dots acrossthe surface of the object during an exposure period; and an imagingcapturing relay means to capture a reflection of the pattern from theobject and relay the captured reflection to the image sensor.
 16. Thelaser digitizer of claim 15 where the beam relaying means comprises anoptical relay rod lens.
 17. A method for generating a three-dimensionalvisual image of an in vivo object comprising: generating a multi-axiscollimated beam of light, the collimated beam of light being generatedremotely from the object; scanning the multi-axis collimated beam oflight, from a first position with respect to the object, in a secondpattern, where the pattern includes a plurality of substantiallyparallel curves having curvilinear segments; capturing an image of areflection of the pattern from the object during an exposure period; anddetermining a map of the surface of the object based on the capturedimage.
 18. The method of claim 17 where the act of scanning furthercomprises relaying the multi-axis collimated beam of light to an objectin oral cavity.
 19. The method of claim 17 further comprising the actsof: scanning the multi-axis collimated beam of light, from a secondposition with respect to the object, in a predetermined pattern, wherethe pattern includes a plurality of substantially parallel curves havinga curvilinear segments; capturing an image of a reflection of thepattern from the object in the second position; and merging the capturedimage from the first position with the captured image from the secondposition.
 20. The method of claim 17 where the second pattern issubstantially similar to the first pattern.